Are laptops powerful enough to run this software comfortably or would I be better off with a more powerful desktop? I was thinking of getting a good MacBook Pro when the new ones come out, so would a good speced one be up to the job?

Where CPU power and speed matter is when using lots of plugins and lots of tracks (like far more than 32 tracks).

If you will be using the Cubase AI that came with your Motif and no softsynths or effect plugins other than the provided ones, you will have no problems.

However, since owners can no longer replace the RAM or disk on new MacBooks, keep in mind the age old advice: always buy the fastest computer with the most memory and largest drive that you can afford.

I have a MacBook Pro 17 “ and Cubase Studio 5.
I use also plug-ins (Real Guitar + Native instruments Komplete 8 and others).
This works fine (plug-ins were limited to 4 or 5 tracks, I did not need more…)
Some remarks :
-Plug-ins with samples will take a lot of power, so if I should add a lot of instruments which are available from the libraries (in real time) I could get problems I presume. Of course you can record one track at the time which can be heavily loaded with samples without problem.
-Midi has never been a problem as it gives the work to the workstations.Midi takes only a few percentages of your capacity.
First conclusion : if I want to manage midi, steering the motifs or other workstations it is never a problem because the data-transfer is only midi (as said before, this is very minimal even for an old computer)

Second conclusion : once you go to plug-ins it becomes very much harder because your computer has to manage this and play the samples. The difference in work for the computer is VERY big. You can see that on the volume of a midi-file (mostly less than 500 kb). Once you go to samples it becomes very fast several megabytes.

Last conclusion : Mac or Windows don’t give me a significant difference (there are since years always discussions about this).
But : if you work on a MacBook or a Windows portable you will always encounter problems with switching.
I suppose that you don’t use both platforms, but if you use only one (Windows or Mac portables) you have to take great care about the “take away” (I mean : stop -disconnect the ports-move the installation-connect again all cables-startup).

If you work with a portable, I suppose that you go to another place and want the config as soon as possible again.

Here I think the Mac is more practical : it smells the config very good
But if you don’t switch, there is no big difference…

BTW there is an alliance between Yamaha & Steinberg Cubase ! They know each other very well

Sorry, forgot to tell you, but meaby you understood already that the OSX is in your case not important.
You will get no better sound or important facilities with the latest OS version.
Today there is a market for “all-in” with a lot of simple alternatives which will take you away from your creative possibilities.
Sans rancune…My open opinion

once you go to plug-ins it becomes very much harder because your computer has to manage this and play the samples.

I suppose that you don’t use both platforms, but if you use only one (Windows or Mac portables) you have to take great care about the “take away” (I mean : stop -disconnect the ports-move the installation-connect again all cables-startup).

Just some comments about those statements.

Sample based plugins are not really the most CPU hungry. It’s the streaming of the samples off the disk that can be an issue, not the CPU load.

The compute-intensive plugins are those that do a lot of high definition modeling, such as synthesizers allowing audio rate modulations or effects processors like linear phase EQs.

As far as connecting and disconnecting devices, this is a really big deal with Windows. For some reason when Windows first encounters a device on a given USB port, if it ever sees the same device connected to a different USB port it sees it as a different device! So be obsessive about always connecting your devices to the same USB ports every time. Mac does not have this problem but that doesn’t mean you should randomly connect your devices to different USB ports just for the hell of it!

On both platforms, neverconnect or disconnect devices while the computer is running and especiallynot when your DAW is running! Always connect and power on the external devices first before booting the computer and do not disconnect until after you have shut down. Do not let the computer go to sleep while devices are connected! This caused me many problems with Windows, Mac only once in a while.

Something to consider: If your vintage keyboard requires a Firewire board to provide sound (as does the Motif XF), most newer PC laptops can’t support Firewire due to lack of Firewire ports or space to add Firewire boards. I have a new thin laptop which I use USB for MIDI only connection to the Motif. I may put one of my spare desktop machines into service after adding an inexpensive Firewire card.

I’ve just upgraded from Cubase 5 to Cubase 10 - quite a jump. The biggest thing to note is that C10 is only 64bit and will need a 64 bit OS to run on.

Re desktop vs laptop - its a question of portability vs space for extras - extra drives, extra cards, extra RAM etc. A laptop you can take with you - desktop you can’t - but it is far easier and cheaper(?) to upgrade a desktop to stay in line with increased needs.